/*
 * Copyright (c) 2011-2012 Alexander Dubu
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * o  Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * o  Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * o  Neither the name Axil nor the names of its contributors may be used to
 *    endorse or promote products derived from this software without specific
 *    prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package axil.api.extend;

import axil.api.AxilObject;
import axil.api.Configuration;
import axil.api.Context;
import axil.api.Persona;

import java.io.Writer;


/**
 * An object representing the current execution environment for a script. The
 * environment contains the context and other run-time information.
 * <p/>
 * This interface is not intended to be implemented by host applications. This
 * interface provides a mechanism for encapsulating the implementation. Use the
 * Axil.instance() object to access instances of this object.
 */
public interface Environment {
	/**
	 * Get a constant from the run-time environment by its unique identity. This
	 * is safe to invoke at any time, since the Axil compiler has already
	 * verified that the constant exists.
	 *
	 * @param ident
	 * 	The unique identity of the constant. The string given cannot be null or
	 * 	empty.
	 *
	 * @return
	 * 	Returns a non-null Axil object. If the constant does not exist, then an
	 * 	exception is thrown.
	 */
	public AxilObject constant(String ident);


	/**
	 * Get an object from the context. The entire context chain is traversed,
	 * if necessary, starting from the top-most context.
	 *
	 * @param ident
	 * 	The identity of the root object. For example, for the host application
	 * 	object reference "Shopping-Cart.Items", the string "Shopping-Cart" would
	 * 	be given, not the full reference.
	 *
	 * @return
	 * 	Returns a non-null Axil object. If the object does not exist, then an
	 * 	exception is thrown.
	 */
	public AxilObject context(String ident);


	/**
	 * Access the context associated with this script execution.
	 *
	 * @return
	 * 	Returns the context, which is never null.
	 */
	public Context context();


	/**
	 * Get the current configuration associated with the execution of the
	 * script. The configuration returned has already been validated for
	 * correctness and sealed from modified.
	 *
	 * @return
	 * 	Returns the current configuration, which is never null.
	 */
	public Configuration configuration();


	/**
	 * Get the persona associated with the execution of the script.
	 *
	 * @return
	 * 	Returns a non-null persona. If an explicit persona was not previously
	 * 	provided, then a system persona will be automatically substituted.
	 */
	public Persona persona();


	/**
	 * Get a handle to the output stream where any print() expressions from the
	 * script will write their output.
	 *
	 * @return
	 * 	Returns a non-null output stream. Even if output is disabled, a non-null
	 * 	(data sink) object is returned.
	 */
	public Writer output();
}
